Abstract

Lithium cathode materials have been considered as promising candidates for energy storage applications because of their high power/energy densities, low cost, and low toxicity. However, the Li/Ni cation mixing limits their application as practical electrode materials. The cation mixing of lithium transition-metal oxides, which was first considered only as the origin of performance degeneration, has recently been reconsidered as a way to stabilize the structure of active materials. Here we find that as the duration of the post-synthesis thermal treatment (at 500 °C) of LiNi1/3Co1/3Mn1/3O2 (NCM) was increased, the Li/Ni molar ratio in the final product was found to decrease, and this was attributed to the reduction in nickel occupying lithium sites; the cation mixing subtly changed; and those subtle variations remarkably influence their cycling performance. The cathode material with appropriate cation mixing exhibits a much slower voltage decay and capacity fade during long-term cycling. Combining X-ray diffraction, Rietveld analysis, the Fourier transform infrared technique, field-emission scanning electron microscopy, and electrochemical measurements, we demonstrate that an optimal degree of Ni2+ occupancy in the lithium layer enhances the electrochemical performance of layered NMC materials and that this occurs through a “pillaring” effect. The results provide new insights into “cation mixing” as a new concept for material design utilization of layered cathodes for lithium-ion batteries, thereby promoting their further application in lithium-ion batteries with new functions and properties.

Authors contributing to RSC publications (journal articles, books or book chapters)
do not need to formally request permission to reproduce material contained in this
article provided that the correct acknowledgement is given with the reproduced material.

Reproduced material should be attributed as follows:

For reproduction of material from NJC:
Reproduced from Ref. XX with permission from the Centre National de la Recherche
Scientifique (CNRS) and The Royal Society of Chemistry.

For reproduction of material from PCCP:
Reproduced from Ref. XX with permission from the PCCP Owner Societies.

For reproduction of material from PPS:
Reproduced from Ref. XX with permission from the European Society for Photobiology,
the European Photochemistry Association, and The Royal Society of Chemistry.

For reproduction of material from all other RSC journals and books:
Reproduced from Ref. XX with permission from The Royal Society of Chemistry.

If the material has been adapted instead of reproduced from the original RSC publication
"Reproduced from" can be substituted with "Adapted from".

In all cases the Ref. XX is the XXth reference in the list of references.

If you are the author of this article you do not need to formally request permission
to reproduce figures, diagrams etc. contained in this article in third party publications
or in a thesis or dissertation provided that the correct acknowledgement is given
with the reproduced material.

Reproduced material should be attributed as follows:

For reproduction of material from NJC:
[Original citation] - Reproduced by permission of The Royal Society of Chemistry (RSC) on behalf of the
Centre National de la Recherche Scientifique (CNRS) and the RSC

For reproduction of material from PCCP:
[Original citation] - Reproduced by permission of the PCCP Owner Societies

For reproduction of material from PPS:
[Original citation] - Reproduced by permission of The Royal Society of Chemistry (RSC) on behalf of the
European Society for Photobiology, the European Photochemistry Association, and
RSC

For reproduction of material from all other RSC journals:
[Original citation] - Reproduced by permission of The Royal Society of Chemistry

If you are the author of this article you still need to obtain permission to reproduce
the whole article in a third party publication with the exception of reproduction
of the whole article in a thesis or dissertation.

Information about reproducing material from RSC articles with different licences
is available on our Permission Requests page.